A permanent magnet brush motor usually comprises a stator and a rotor. The stator comprises a housing and permanent magnets mounted to the inner surface of the housing. The rotor comprises a rotating shaft, a magnetic core and a commutator fixed to the rotating shaft, and a rotor winding wound around the magnetic core. There exists the tooth-slot effect between the stator and the rotor. In some applications, it is expected that the motor has a larger cogging torque. For example, for roller shutter motors, it is desirable to increase the cogging torque of motor so that the motor can stop the shutter at any designated positions without additional brake devices to thereby simplify the structure and reduce the cost of the roller shutter.